Are fingerprints really infallible, unique ID?

How unique are your fingerprints? It's general held (and as er, The Register confidently stated just yesterday) that your fingerprints being found at the scene of the crime tied you up with it pretty conclusively, but a report published earlier this year by New Scientist claims that there is little scientific basis for the infallibility of fingerprints, and that the only research indicating that there is, is fatally flawed.

This could have major implications for the criminal justice system, and could undermine the basic premise of planned ID sytems in the UK, US and Europe. The report notes that the only known study, commissioned b y the US Department of Justice and only made public in summary form, was challenged in December. The study involved matching up 50,000 fingerprint images, and concluded from this that the probability of a false match was effectively zero. However, says New Scientist, "Although this produced an impressive-sounding 2.5 billion comparisons, critics point out that it is hardly surprising that a specific image should turn out to be more like itself than 49,999 other images."

The study wasn't designed to test matches between two or more different prints from the same finger, and it was even discovered that it originally included three instances of fingerprints being listed as similar but different, when they were actually different prints from the same finger. One pair was even found to be as dissimilar as prints from different people. And the sample size is seen by many critics as being too small to be seen as valid.

Despite the apparently shaky foundations of the little 'proof' that exists, there seems to be no government enthusiasm for further research. The DoJ has refused to sanction further research, and a Department of Defense and National Institute of Justice programme fell apart last year after arguments over dissemination and review of the material.

New Scientist points out that fingerprint evidence still has a value, but that it's such a long-standing technique that it has never been subjected to rigorous scientific scrutiny. This could well be its undoing, as ID systems' need to match up prints from millions of people takes fingerprinting into entirely uncharted territory. It would surely be just a little bit embarrassing if a few years down the line governments' deployment of fingerprints in the war on terror resulted in the near overthrow of the criminal justice system, wouldn't it? ®